Merge "Prevent callback registration when back flag is disabled" into tm-dev am: 1c6de844

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/18794217



Change-Id: I8054556537104bb80d940272b367ed9b8ffa520c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>